The deaths of three Canadians,
all killed this fall shortly after being shot by police
with stun guns, have drawn renewed attention to the
safety of the "non-lethal" devices.

Claudio Castagnetta, an Italian
immigrant, died in Quebec City on September 21 after
being shot by police with a Taser on September 18. Robert
Dziekanski, a Polish immigrant just arriving in Canada,
died at the Vancouver International Airport minutes
after being shot with a Taser early October 15. Quilem
Registre died in a Montreal hospital on October 18 after
being Tasered during a drunk-driving arrest four days
earlier. The number of deaths over such a short period
of time  along with 14 other Canadian deaths after
Taser shocks since 2003  has led to calls from
the public for reconsideration of police's use of the
stun guns, and they're looking to physicians to provide
answers. But those answers have thus far been elusive.

Dr John Butt, a forensic pathologist,
says understanding the reasons for the death of Mr Dziekanski,
the most high-profile victim because he died in public
at the airport shortly after being shot with a Taser,
will be a challenge. Was it caused by the shock, or
due to his reportedly "agitated" state (though no drugs
or alcohol were found in a post mortem tox report),
some trauma suffered when he was restrained, or a combination
of these factors? "I don't think you're going to get
a very good answer to that question because you can't
experiment," says Dr Butt, who has looked at deaths
from conducted electricity devices (CEDs) in the past.
He suggests the repeated shocks from a stun gun could
have played a role in the man's death. He concluded
as much in 2005 when asked to review the medical literature
for a BC Police Complaints Commission report on CEDs.
Too many shocks could arrest respiration and should
be avoided, says Butt, but more studies need to focus
on the still poorly understood physiology of people
suffering from a controversial condition called "excited
delirium."

DELIRIUM
DISPUTE
In 2005, a pair of Chicago physicians wrote a letter
to the editors of New England Journal of Medicine
claiming that CEDs can cause ventricular fibrillation
(VF). They had recently treated a 14 year-old boy who
had gone into VF after being shocked with a Taser stun
gun. The boy was resuscitated by paramedics at the scene,
but the letter attracted international interest.

Medical advisors to the weapon's
manufacturer, Taser International, said the doctors'
report was "speculative and not backed by scientific
evidence." Dr Mark Knoll, Taser International's scientific
and medical board chair, told NRM by email that the
authors of the letter should have known better than
to go off half-cocked. The company has blamed the boy's
medical crisis on metabolic acidosis resulting from
"excited delirium"  a vague, drug intoxication-related
diagnosis often cited by Taser International. But the
condition doesn't appear in any psychiatric literature
or diagnostic guides; the American Civil Liberties Union
has called excited delirium a method of "whitewashing"
in-custody deaths. Taser International insists illicit
drug use can cause excited delirium, which increases
the risk of adverse events from the shock, including
death. Indeed, all three recent cases in Canada have
involved allegations of intoxication. None of those,
however, have been proven.

HEART
SHOCKS
The medical literature on stun gun-induced VF has demonstrated
that it can occur, but that it's highly unlikely. "In
my mind it's not an issue," says John Webster, PhD,
a professor of Biomedical Engineering at the University
of Wisconsin who has studied the question. Using pigs
as subjects, Dr Webster measured how close to the heart
the barb from a stun gun would have to be to cause VF.
The result was 17mm and even less when he revised his
method of inserting the barb following criticism from
Taser scientists.

"We've done a lot of work trying
to estimate the probability that a human could die of
ventricular fibrillation," explains Dr Webster. "It's
a few per million kind of thing. You've got to have
a very thin person with a dart between his ribs right
over his heart."

Chicago cardiologist Dr Wayne Franklin,
one of the authors of the 2005 NEJM letter that
is responsible for much of the current controversy,
declined to comment. Though he insists it's "an extremely
important issue," he says his lawyers have told him
not to speak to the press.